The invention is concerned with a device for the movement and positioning of an element in space.
The majority of devices of the above type which are known, such, for example, as the main known industrial robots, include a carrier member which supports a wrist, the carrier member having three axes known as the main axes, intended for defining three degrees of freedom which may be rotations and/or translations, so as to position the wrist in space, the orientation of the said wrist being in turn controlled by one to three axes known as the secondary axes, in accordance with one to three supplementary degrees of freedom which are necessarily rotations.
In these devices, the configuration of the carrier member of which may be of cartesian type having cylindrical coordinates or spherical coordinates or of SCARA (Selective Compliance Assembly Robot) type or having angular coordinates, the control of the degrees of freedom is effected in series. The first main axis is employed as a reference for the motion of the second main axis, the latter serving as a reference for the motion of the third main axis which in turn serves as a reference for the degrees of freedom which define the orientation of the wrist.
The configuration in series necessitates the location of the driving motors at the level of each axis or demands a heavy and complicated configuration for the transmission of the motion to the axes, and, consequently, even in the case of the movement of a small load, large masses must be set in motion.
On the other hand a device is known having a configuration similar to that of a flight simulator, having six axes working in parallel. In this case, the motors may be fixed, which limits the masses to be set in motion. This species of device, however, enables only a very restricted working volume to be reached.
A device in which the control of the three basic degrees of freedom is effected in parallel is described in the patent U.S. Pat. No. 2,286,571. This device is intended for the positioning and t control of the motion of a paint gun. It comprises three actuators integral with one base member, each of the actuators including one fixed portion and one moving arm mounted in rotation at one end of it on the fixed portion of the actuator. On the second end of each of the arms are mounted respectively three linking bars by way of articulations of cardan type mounted respectively at one of the ends of the linking bars. Two of the linking bars are mounted by articulation at their respective second ends onto the third linking bar, near to the second end of it. The support for the gun is mounted by articulation at the end of the third linking bar.
The Patent Application FR-A-2,550,985 describes another device in which the control o the three basic degrees of freedom is effected in parallel. This document concerns an arm able to extend, retract and fold, composed of a plurality of extensible members mounted in series, each of them including three actuators acting in parallel.
The known devices are, however, poorly adapted to the transfer of light pieces at very high rates.